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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_007_421">&nbsp;</a>NAME</h4><blockquote>
log10 - base 10 logarithm function
</blockquote><h4><a name = "tag_000_007_422">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="math.h.html">math.h</a>&gt;

double log10(double <i>x</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_007_423">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>log10()</i>
function computes the base 10 logarithm of
<i>x</i>,
log<sub><small>10</small></sub>(<i>x</i>).
The value of
<i>x</i>
must be positive.
<p>
An application wishing to check for error situations should set
<i>errno</i>
to 0 before calling
<i>log10()</i>.
If
<i>errno</i>
is non-zero on return,
or the return value is NaN,
an error has occurred.
</blockquote><h4><a name = "tag_000_007_424">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>log10()</i>
returns the base 10 logarithm of
<i>x</i>.
<p>
If
<i>x</i>
is NaN, NaN is returned and
<i>errno</i>
may be set to [EDOM].
<p>
If
<i>x</i>
is less than 0,
&nbsp;-HUGE_VAL or NaN is returned,
&nbsp;and
<i>errno</i>
is set to [EDOM].
<p>
If
<i>x</i>
is 0,
-HUGE_VAL is returned and
<i>errno</i>
may be set to [ERANGE].
</blockquote><h4><a name = "tag_000_007_425">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>log10()</i>
function will fail if:
<dl compact>

<dt>[EDOM]<dd>
The value of
<i>x</i>
is negative.

</dl>
<p>
The
<i>log10()</i>
function may fail if:
<dl compact>

<dt>[EDOM]<dd>
The value of
<i>x</i>
is NaN.

<dt>[ERANGE]<dd>
The value of
<i>x</i>
is 0.

</dl>
<p>
No other errors will occur.
</blockquote><h4><a name = "tag_000_007_426">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_427">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_428">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_429">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="isnan.html">isnan()</a></i>,
<i><a href="log.html">log()</a></i>,
<i><a href="pow.html">pow()</a></i>,
<i><a href="math.h.html">&lt;math.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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